1. Field of the Invention
The present invention relates to a very high voltage switch and more specifically to a push-pull switch.
2. Discussion of the Related Art
In prior art, push-pull switches generally contain transistors of complementary types, that is, NPN and PNP bipolar transistors or N-channel and P-channel MOS transistors. This does not enable choosing optimal components when high-voltage switches are desired.
On the other hand, conventionally, when very high voltage switches are desired, components that can withstand as high a voltage as possible are used and this requires manufacturing specific components at high costs.
A first object of the present invention is to provide a push-pull type switch in which all transistors are of the same type.
Another object of the present invention is to provide such a switch likely to withstand very high voltages.
To achieve these objects, the present invention provides a push-pull switch including a first N-channel MOS transistor, the drain-source path of which is connected between a high voltage terminal and an output terminal, a first resistor connected between the gate of the first transistor and the high voltage terminal, a diode having its anode connected to the output terminal and its cathode connected to the gate of the first transistor, a second N-channel MOS transistor having its drain connected to the cathode of the diode, its source connected to a reference potential, and its gate connected to a control terminal, and a second resistor connected between the gate of the second transistor and the output terminal.
According to an embodiment of the present invention, each of the MOS transistors has its source connected to its substrate.
According to an embodiment of the present invention, a third resistor is arranged in series with the gate of the second transistor, the second terminal of this third resistor being connected to the second resistor and to a protection diode having its second terminal connected to the reference diode.
According to an embodiment of the present invention, each of the first and second transistors is replaced with a chain of series transistors, and each of the first and second resistors is replaced with a corresponding chain of resistors, the resistors of each of the chains being equal, fourth equal resistors being connected between the gates of the transistors connected to the high potential and fifths resistors being connected between the gates of the transistors connected to the low voltage.
The foregoing objects, features and advantages of the present invention will be discussed in detail in the following non-limiting description of specific embodiments, in conjunction with the accompanying drawings.